The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 14, 1992
Filed:
Nov. 26, 1990
Helmut Foell, Munich, DE;
Volker Lehmann, Munich, DE;
Siemens Aktiengesellschaft, Berlin and Munich, DE;
Abstract
For a two-stage measuring method, a respective cell having an electrode therein is applied to the front surface and to the rear surface of a semiconductor wafer, whereby only the cell as the rear surface is filled with an electrolyte in the first measuring step. The minority carrier photo current I.sub.2 ' flowing between the electrode and the semiconductor surface in the rear cell, given illumination of the front cell of the semiconductor crystal wafer, is dependent on the recombination speed S at the front surface. In the second measuring step, the front cell is also filled with electrolyte and both the rear surface photo current I.sub.2, given what is now a negligible influence of the value S as well as the front surface photo current I.sub.1 are measured. The recombination speed S can be calculated from the measure photo currents with the assistance of a mathematical equation. Given point-by-point illumination and scanning over the crystal wafer, the topical distribution of the recombination speed is obtained.